This invention relates generally to vapor compression air conditioning systems, and more particularly to improved system efficiency related to the exterior heat exchange coil by cleaning and cooling the coil.
Typical refrigeration systems include a compressor, a motor adapted for driving the compressor, a condenser in fluid communication with the compressor, an expansion device in fluid communication with the condenser and an evaporator in fluid communication with the expansion device. Refrigeration systems of this type used for air conditioning and dehumidification remove moisture from the air at the evaporator. The moisture condensed at the evaporator is called condensate and is essentially distilled water.
In an air conditioning system of the aforementioned type, waste heat is transferred to the outside environment at the condenser through use of a heat exchange coil. This coil is comprised of a plurality of refrigerant tubes connected to and supported by metal fins. These metal fins aide in the heat dissipation from the refrigerant. This heat exchange is normally aided by a fan designed to force ambient air past the heat exchange coils and fins.
After a period of service the heat exchange coil and fins accumulate dust, dirt and foreign matter that act as an insulative coating. This coating restricts the flow of heat between the refrigerant inside the coils and the air flowing past the coils and fins. The result is that the overall system efficiency is degraded.
A second problem which arises when the heat exchange coils and fins become and remain coated with foreign matter is corrosion on the surface that further insulates and restricts the flow of heat. This is a particular problem in coastal areas where ocean salts accumulate on the metal coils and fins.
When in service in proximity to a manufacturing or industrial facility, air conditioning heat exchange coils tend to accumulate a coating of materials being dispersed into the air by the manufacturing process. Industrial by-products such as paper pulp and coal ash will form a thick layer on exposed coils and fins, sometimes completely blocking the air flow through the coil.
Air conditioner manufacturers specify regular coil cleanings as part of a system's maintenance program. In practice, however, the exterior heat exchange coil seldom receives any attention until a breakdown occurs or system efficiency degrades to a noticeable degree. At that point the system has been operating inefficiently for some time, wasting energy and corrosion may already have had a permanent effect on the surface of the coils and fins.
For these and other reasons it is desirable to clean the exterior condenser heat exchange coil frequently.
The industry has long dealt with condensate water as purely a waste product and has many methods and apparatus for its disposal. In many residential installations condensate is simply piped into a French drain, sump pump or floor drain. The constant source of standing water in a house can cause or irritate existing health problems related to mold allergies.
The Environmental Health Center, a Division of the National Safety Council, says that exposure to molds "may trigger allergic reactions, including hypersensitivity to pneumonia, allergic rhinitis and some types of asthma." They also state that "some molds and mildews can release disease causing toxins. These toxins can damage a variety of organs and tissues in the body, including the liver, central nervous system, digestive system and immune system. Some diseases, like humidifier fever, can be traced to microorganisms that grow in home heating and cooling systems." They recommend relative humidity levels between 30% and 50% to help prevent mold growth.
Some other residential installations deal with the waste condensate by piping it into the building's sanitary sewer drain. Some municipalities (example: Burlington County, N.J.) have banned this practice stating the increased load it places on waste water treatment facilities.
Roof mounted commercial air conditioners deal with waste condensate by dumping it directly onto the roof. This practice on buildings with flat roofs frequently produces pools of standing water that increase roof leaking problems and provide breeding grounds for harmful insects.
Some inventions have detailed different methods of condensate disposal. U.S. Pat. No. 5,461,879 illustrates a method of condensate removal by splashing the water from a collection tray onto the condenser coil from the inside for evaporation. This and other inventions of its type concentrate merely on getting rid of the waste water without deriving much benefit from its use.
U.S. Pat. No. 5,682,757 describes a method of piping condensate water to specific mechanical and electrical components of the air conditioning system for direct cooling of said components. This invention requires that the condensate piping be built into the air conditioner at its manufacture and therefore cannot be retro-fitted to existing units. It also does not deal with cleaning the exterior condenser heat exchange coil.
Still some other patents describe apparatus for cleaning the coils of window mounted air conditioners such as U.S. Pat. No. 4,884,416. Again these devices are designed to be included in the air conditioner at its manufacture and cannot easily be retro-fitted to existing units. Still another problem with these devices is the large number of moving parts required for their operation. This, it seems, would provide another step in the routine maintenance of the air conditioning unit.